1. Field of the Invention
The present invention relates to a rotor, having a plurality of magnetic poles, of a rotating electrical machine and to a manufacturing method for the rotor.
2. Description of the Related Art
With regard to a rotor, of a rotating electrical machine, having a plurality of permanent magnets on the circumferential surface of a laminated iron core fixed on the circumferential surface of the rotor shaft, a configuration has already been proposed in which both axis-direction ends of each of the permanent magnets are covered with a cover of a non-magnetic material (e.g., refer to Patent Document 1).
In the conventional rotor of a rotating electrical machine, hereinafter) disclosed in Patent Document 1, the non-magnetic cover provided on the rotor is fixed on the permanent magnet, by means of an adhesive. With the conventional rotor of a rotating electrical machine configured in this manner, the position, in the circumferential direction of the rotor, of the permanent magnet can securely be fixed, by fixing the laminated iron core and the permanent magnet to each other and by fixing the permanent magnet and the cover to each other.
In addition, as another conventional rotor of a rotating electrical machine, a configuration has already been disclosed in which permanent magnets are arranged on the circumferential surface of a yoke, the outer surfaces of the permanent magnets are covered with a fastening ring of a non-magnetic material, and the fastening ring is pressed and fixed by a fixation member such as a bolt to the yoke, in a direction from the circumference to the radial inside of the yoke (e.g., refer to Patent Document 2).
With the conventional rotor of a rotating electrical machine disclosed in Patent Document 2, the fastening ring is pressed into the yoke from the circumference of the yoke and binding force is exerted on the permanent magnet, so that the position, in the circumferential direction, of the permanent magnet is secured.
[Patent Document 1] Japanese Patent Laid-Open No. 2001-25193
[Patent Document 2] Japanese utility model Laid-Open No. S55-120285
In the case of the conventional rotor of a rotating electrical machine disclosed in Patent Document 1, while the adhesive hardens or when the adhesive does not have sufficient fixing power, the position, in the circumferential direction, of the permanent magnet cannot securely be fixed. The position, in the circumferential direction, of the permanent magnet considerably affect the cogging torque of the rotating electrical machine; therefore, there has been a problem that, in the case where the position, in the circumferential direction, of the permanent magnet cannot be fixed at a predetermined position, deterioration or fluctuation in the cogging torque is caused, whereby vibration or noise occurs in the rotating electrical machine.
Moreover, in the case of the conventional rotor of a rotating electrical machine disclosed in Patent Document 2, a fixation member, such as a bolt, for fixing the fastening ring is required; therefore, the increase in material costs, processing costs and the like is caused. Still moreover, it is required to make the space between the permanent magnets larger than the size of the fixation member; thus, the torque is deteriorated unless the physical constitution of the rotating electrical machine is changed. Furthermore, compensation of the torque deterioration causes the physical enlargement of the rotating electrical machine, for example, the extension of the shaft of the rotating electrical machine.